This invention relates to a two cycle internal combustion engine, particularly to a two cycle internal combustion engine having improved power performance and decontamination efficiency of exhaust gas.
In the two cycle engine constituted with a scavenging port and an exhaust port formed on the side surface of a cylinder and having a mechanism in which these ports are closed and opened by a piston, after burst of mixture of fuel and air the exhaust port is opened when the piston descended to a certain position and then discharge of the combusted gas is initiated by the internal pressure of the cylinder. When the piston descended further to the next position, the scavenging port is opened, thereby fresh mixture compressed in a crank chamber flows into and fill the cylinder by scavenging the combusted gas remaining in the cylinder. When the piston turned to ascending, first the scavenging port is closed and then the exhaust port is closed to complete the change of gas in the cylinder.
This type of two cycle engine has a defect that the amounts of discharge of CO (carbon monoxide) and HC (hydrocarbon) are high, because a part of both the combusted gas containing CO and the mixture containing HC flowed in from the scavenging port is exhausted from the exhaust port into the atmosphere. To improve the defect mentioned above, it is essential to install an additional cleaning device such as a catalytic converter in the exhaust system to decontaminate the exhaust gas by reprocessing HC and incompletely combusted gas.
Thus, it is desirable for improvement of the decontamination efficiency of the exhaust gas to conduct a concentrate post-treatment by separating and trapping only the exhaust gas containing large amounts of hazardous components to be treated such as HC, CO and the like.